Radiographic evaluation of mandibular third molars: an ex vivo comparative study between multilayer and conventional panoramic radiography.

OBJECTIVES: To compare the multilayer panoramic radiography (MPAN) and conventional panoramic radiography (CPAN) in the evaluation of mandibular third molars using cone-beam computed tomography (CBCT) as a reference. METHODS: CPAN, MPAN, and CBCT scans from 33 dry human mandibles were acquired using the OP300 Maxio unit, totalizing 56 mandibular third molars to be evaluated. Three examiners evaluated each third molar according to their position, depth of impaction in the mandibular ramus, proximity between the dental root apexes and the mandibular canal, and the presence of radiographic signs of proximity to the mandibular canal. In addition, when there was a distance between the root apexes and the mandibular canal, it was measured. As a reference, these same parameters were assessed in the CBCT scans by a fourth examiner. For the statistical analysis, the weighted Kappa, Bland Altman, and Wilcoxon tests were performed (α = 0.05). RESULTS: The agreement between the assessments performed in the panoramic modalities with the CBCT ranged from 66.1% to 100.0% for the categorical variables. Overall, the agreement values of CPAN and MPAN with CBCT were similar. The distances between the dental root apex and the mandibular canal for both CPAN and MPAN were significantly underestimated compared to CBCT (p < 0.05). The intra- and interexaminer agreements of the examiners ranged from poor to almost perfect; in general, the agreements were higher in the evaluation performed in the MPAN than in the CPAN. CONCLUSIONS: The MPAN performs similarly to CPAN for evaluating mandibular third molars and their proximity relationship to the mandibular canal. CLINICAL RELEVANCE: Preoperative evaluation of lower mandibular third molars is usually performed using CPAN. Recently, a new tool, MPAN, was developed, which has not yet been tested for the evaluation of mandibular third molars and showed similar performance to CPAN in the present study. Future studies using MPAN are encouraged to evaluate other diagnostic tasks.

Artifacts caused by titanium implants in CBCT images of the mandible: an experimental study.

This study evaluated the quantity of metal artifacts produced by dental implants placed in different mandibular regions using various cone beam computed tomography (CBCT) protocols. Titanium implants were placed in 4 regions (incisor, canine, premolar, and molar) of an artificial mandible and subjected to CBCT examinations with the mandibular model placed in different positions within the field of view (FOV) and imaged with different FOV and voxel sizes. An axial section of the cervical region of each implant was selected for artifact quantification. The artifacts were measured by normalizing the actual standard deviation (ASD) of the voxel values. Kruskal-Wallis and Student-Newman-Keuls tests were used to compare the tooth regions and the different positions of the mandible. The Wilcoxon test was used to compare changes in FOV and voxel size. The intraobserver agreement was calculated using the intraclass correlation coefficient. The significance level was 5%. The incisor region showed significantly more artifacts than other regions (P = 0.0315). No statistically significant difference was found when the position of the mandible varied within the FOV (P = 0.7418). Smaller FOV and smaller voxels produced more artifacts (P < 0.0001). The quantity of metal artifacts was affected by FOV and voxel size as well as by anatomical region. Variation of the mandible location within the FOV did not affect the artifacts as defined by the normalized ASD of the voxel values.

Do the dimensions of the hard palate have a relationship with the volumes of the upper airways and maxillary sinuses? A CBCT study.

BACKGROUND: As the hard palate is a central structure of the skull, and its close relationship with the nasal cavity, oral cavity, and maxillary sinuses, it would be of interest to study if there is a relationship between this bone and other structures of the stomatognathic system. Thus, this study aimed to assess the dimensions of the hard palate and associate them with sex, and skeletal and breathing patterns. Also, to investigate if there is a relationship between these dimensions and the volumes of the upper airways and maxillary sinuses. METHODS: Two hundred and ninety-eight CBCT scans of patients were classified according to sex, and skeletal and breathing patterns. Then, the linear dimensions of width and height of the hard palate at the regions of the first premolars and first molars, and the volumes of the upper airways and maxillary sinuses were measured using the CS 3D Imaging and ITK-SNAP software, respectively. Data were submitted to multi-way analysis of variance and linear regression, with a significance level of 5% (α = 0.05). RESULTS: Sex and facial type influenced the hard palate dimensions (p < 0.05). Males had greater width and height of the hard palate than females (p < 0.0001). It was observed greater width for brachycephalics at the first premolars region (p = 0.0032), and greater height for dolichocephalics at the first premolars (p = 0.0154) and first molars (p = 0.0038) regions. Skeletal malocclusion and breathing pattern did not influence the measurements of the hard palate (p > 0.05). There was a significant relationship between the width and height of the hard palate at the premolar's region and the total volume of the upper airways (p = 0.018, and p = 0.038), and between both dimensions of the hard palate at the molar's region and the total volume of the maxillary sinuses (p < 0.0001). CONCLUSIONS: The hard palate dimensions are influenced by sex and facial type, but not by skeletal malocclusion or breathing pattern. Also, there is an association between these dimensions and the volumes of the upper airways and maxillary sinuses.

Quantitative assessment of artefacts and identification of gaps in prosthetic crowns: a comparative in vitro study between periapical radiography and CBCT images.

OBJECTIVES: To evaluate, in an in vitro study, the quantity of artefacts generated by two different restorative materials, and to determine the diagnostic accuracy of cone beam CT (CBCT) scans and periapical radiographs in identifying gaps in prosthetic crowns. METHODS: A total of 30 teeth restored with metal-ceramic (n = 15) and all-ceramic (n = 15) crowns, properly adapted and with 0.30- and 0.50 mm gaps, underwent CBCT exams (with voxel sizes of 0.25 and 0.30 mm) and periapical radiographs. The artefacts generated by two different crowns were quantified and compared by the Mann-Whitney test. In addition, five examiners evaluated the presence or absence of gaps in periapical radiographs and CBCT images. The accuracy of tests was determined by the area under the receiver operatring characteristic curve and these values were compared by using the Kruskal-Wallis test. RESULTS: There was no significant difference in artefact values between the different restorative materials and the different resolutions of CBCT images. Regarding the accuracy of the tests evaluated, periapical radiography and CBCT with voxel size 0.25 mm showed the best performance for smaller gaps (0.30 mm). For larger gaps (0.50 mm), all exams tested showed the same performance. CONCLUSIONS: Periapical radiography was still the most cost-beneficial method for the diagnosis of maladaptation in dental restorations. CBCT exams did not improve accuracy in detecting gaps in prosthetic crowns.

Tomografia computadorizada de feixe cônico como método de avaliação da pneumatização da articulação temporomandibular / Cone-beam computed tomography as a method of evaluating pneumatization of the temporomandibular joint

Introdução: A pneumatização, considerada um processo fisiológico, são cavidades cheias de ar no interior dos ossos do crânio resultante de áreas de células epiteliais. Objetivo: Determinar a prevalência de pneumatização na fossa articular (PFA) e da eminência articular (PEA) do osso temporal por meio de exames de tomografia computadorizada de feixe cônico (TCFC). Material e métodos: Trezentas e noventa imagens de articulações temporomandibulares foram avaliadas por dois examinadores, devidamente calibrados, com experiência em imagens de TCFC. Nos casos em que foi detectada pneumatização, esta foi classificada de acordo com o tipo (unilocular e multilocular) e lateralidade (unilateral ou bilateral). Resultados: A PFA ou a PEA foi diagnosticada em 97 (49,74%) pacientes. Destes pacientes, 61 (31,3%) apresentaram PFA e 36 (18,5%) PEA. Em relação à lateralidade, na PFA, 36 (59%) apresentaram a condição unilateralmente e 25 (41%) bilateralmente. Dentre os pacientes com PEA, 24 (66,7%) apresentaram a condição unilateralmente e 12 (33,3%) bilateralmente. A pneumatização foi correlacionada entre os lados pelo coeficiente de correlação de Spearman e foi significativa para os casos multiloculares (fossa articular: rs=0,52 / p<0,0001 e eminência articular: rs=0,42 p<0,0001). Conclusão: A pneumatização da região temporomandibular é uma característica relativamente comum e, apesar de não necessitar de tratamento, a observação é fundamental para evitar complicações do tratamento ou diagnóstico errôneo na região.

Introduction: Pneumatization, considered a physiological process, are air-filled cavities within the skull bones resulting from areas of epithelial cells. Objective: To determine the prevalence and characteristics of pneumatization of the glenoid fossa and articular eminence on cone beam computed tomography. Material and methods: Images of 195 patients (195 temporomandibular joints) were evaluated and the age and gender of the individuals were collected. In cases where pneumatization was detected, this was classified according to type (unilocular and multilocular) and laterality (unilateral or bilateral). Results: The pneumatization of the glenoid fossa and articular eminence were diagnosed in 63 (32.3 %) patients. Of these patients, 61 (31.3%) had pneumatization of glenoid fossa and 36 (18.5%) had pneumatization of articular eminence. Regarding laterality, in PGF 36 (59%) presented the condition unilaterally and 25 (41%) bilaterally. The patients with PAE, 24 (66.7%) presented the condition unilaterally and 12 (33.3%) bilaterally. Pneumatization was correlated between the sides using the Spearman correlation coefficient and was significant for multilocular cases (glenoid fossa: rs= 0,52/p<0,0001 and articular eminence: rs=0,50 p<0,0001). Conclusion: The pneumatization of temporomandibular region is a relatively common feature, and even though it does not require treatment, observation is crucial to avoid complications of treatment or wrong diagnosis in the region.

Effect of anatomical region on the formation of metal artefacts produced by dental implants in cone beam computed tomographic images.

OBJECTIVES: To quantitatively compare metal artefacts produced by implants in different maxillomandibular regions on cone beam CT (CBCT) images. METHODS: A total of 200 implants selected from CBCT examinations were divided into four groups: Group 1 (n = 50)-implants located in the anterior maxilla; Group 2 (n = 50)-implants located in the posterior maxilla; Group 3 (n = 50)-implants located in the anterior mandible and Group 4 (n = 50)-implants located in the posterior mandible. The implants were further classified as isolated or adjacent to other implants. Three axial reconstructions were selected for each sampled implant (apical, middle and cervical). On each slice, the artefacts produced by the implants were counted. The Mann-Whitney test was used to compare the variables between groups. The Kruskal-Wallis and Student-Newman-Keuls tests were used to compare the axial reconstructions. RESULTS: The mandible showed a greater number of artefacts than the maxilla (apical image: p = 0.0024; middle image: p < 0.0001). The anterior region produced more artefacts than the posterior region (apical image: p = 0.0105; middle image: p < 0.0316). There was no significant difference in the number of artefacts between isolated and adjacent implants, and the cervical image was most affected by artefacts. CONCLUSIONS: Dental implants always produce metal artefacts in CBCT images, and these artefacts are affected by the anatomical location in the dental arch.